HAZOP Guidewords Base Set

HAZARD AND OPERABILITY STUDY GUIDEWORDS FOR FLUID SYSTEMS For each system: 1. Describe function in plant 2. Describe operating conditions 3. Clarify any questions from team

HIGH FLOW HIGH LEVEL Control System Failure Operator Error Downstream/Upstream Pressure Change Two-Phase Flow Power Failure

LOW FLOW LOW LEVEL Control System Failure Operator Error Pump Failure Pipe / Vessel Failure Downstream / Upstream Pressure Change Two-Phase Flow Power Failure

REVERSE FLOW Control System Failure Pump Failure Operator Error Downstream / Upstream Pressure Change Pump Failure Power Failure Zero Flow Backflow Source

HIGH PRESSURE Control System Failure Operator Error Inadequate Pressure Relief / Venting Flashing / Boiling Blockages / Freezing Sedimentation External Fire Decomposition / Gas Evolution Runaway Reaction

LOW PRESSURE Control System Failure Operator Error Condensation / Cooling High Outflow Inadequate Vacuum Relief Power Failure

HIGH TEMPERATURE Control System Failure Operator Error Exothermic Reaction Weather Conditions Heat Source / External Fire Runaway Reaction Power Failure

LOW TEMPERATURE Control System Failure Operator Error Weather Conditions Power Failure

PROCESS CONTROL Adequate? Automatic vs Manual Interlocks, Limits and Trips Critical Variable Monitoring Location

CONTAMINATION Corrosion Products (eg. Salt) Air Ingress Water Ingress Backflow Sediments Biological Activity Raw Material Impurities Reaction By-Products Dust

LOSS OF CONTAINMENT Flanges and Fittings Equipment Failure Sampling Burst Relief Device Human Error Eg. Valve, Cover, Blank etc. left open.

ELECTRICAL SAFETY Area Classification Earthing Static Discharge

MAINTENANCE Isolation Access Delousing / Purging Inspection and Testing Washdown / Cleanup Spares & Availability Experienced Personnel

ISOLATION Method / Hardware Procedures Shutdown Maintenance Breakdown Maintenance Testing Removal / Re-commissioning Lock out procedure when working on equipment

HAZARD AND OPERABILITY STUDY GUIDEWORDS FOR NON FLUID SYSTEMS For each system: 1. Describe function in plant 2. Describe operating conditions 3. Clarify any questions from team

POSITION Too High Too Low Too Far Misaligned Wrong Position

MOVEMENT High Speed Vibration Low Speed Friction No Movement Slip Reverse Movement Jamming & Un-Jamming Vibration Friction Slip Obstacles

LOAD High Load High Flow Low Load Low Flow Loss of Containment

(ELECTRICAL, PNEUMATIC, HYDRAULIC, STEAM) ENERGY (ELECTRICAL, PNEUMATIC, HYDRAULIC, STEAM) Low Energy (Flow, pressure, voltage, current, temperature) High Energy (Flow, pressure, voltage, current, temperature) Energy Failure Reverse (Current, voltage, flow, vacuum)

TIMING Too Late Too Early Too Short Too Long Incorrect Sequence

CONTAMINATION Water Oil Dust Flammables Corrosives Vermin Cleaning

SIZE Too Large Too Small Too Long Too Short Too Wide Too Narrow

PROCESS CONTROL Adequate? Automatic vs Manual Interlocks, Limits and Trips Critical Variable Monitoring Location

MAINTENANCE Isolation Access Delousing / Purging Inspection and Testing Spares & Availability Experienced Personnel

HAZARD AND OPERABILITY STUDY GUIDEWORDS FOR OVERVIEW

TOXICITY Handling Procedures Precautions Exposure Monitoring Emergency Procedures Ventilation

PHYSICAL DAMAGE Degradation of Belt Impact Dropped Objects Transportation Collision Vibration Corrosion Weight (Including Product)

FIRE/EXPLOSION Prevention Systems Detection Systems Fire Protection Emergency Isolation Systems Inert Atmosphere Emergency Procedures

ENVIRONMENTAL IMPACT Vapour Emissions Dust Emissions Effluent Noise Ground Seepage Waste Minimisation

MATERIALS OF CONSTRUCTION Vessels Pipes Pumps Valves Gaskets / Seals Structures Protective Coatings

ACCESS Operation Maintenance Emergency Escape

UTILITIES AND SERVICES Lighting Instrument Air Compressed Air Breathing Air Nitrogen Cooling Water Process Water Steam Fuel Gas Electricity Oxygen Water

COMMISSIONING Requirements Sequence Procedures

START UP First Routine Procedures Philosophy of Control (Supervisory, Automatic, Manual with Interlocks, Manual without Interlocks, Local)

SHUTDOWN Planned Emergency

SAFETY EQUIPMENT Personnel Protection Gas Monitors Breathing Apparatus Safety Showers Barriers / Guards

NATURAL HAZARDS Earthquake Flooding Thunderstorm (Lightning Protection) High Winds

INSPECTION AND TESTING Alarms and Trips Emergency Isolation Valves Gas / Fire Detectors Fire Protection Systems

DEVELOPMENT AND DOCUMENTATION PROCEDURES DEVELOPMENT AND DOCUMENTATION Operations Maintenance Inspection and Testing Confined Space Emergency Engineering Drawings Modification Control

QUALITY CONTROL Inspection and Testing Quality Assurance